Field of the Invention
The present invention elates to a semiconductor device, and more particularly, to a semiconductor device including a power semiconductor element mounted thereon.
Description of the Background Art
A semiconductor device having a resin-sealed power semiconductor element (also called as a transfer-mold power module) is known. The power semiconductor element is mounted on a lead frame, and the lead frame includes a heat sink on the opposite side to the power semiconductor element. In recent years, in order to improve heat dissipation, an insulating sheet with a metal thin film may be disposed on a surface that is in contact with fins of a heat sink.
Due to surge current or surge voltage associated with controlling high voltage and large current at high speed, noise, such as radiation noise and noise terminal voltage, is generated from a power semiconductor element and its terminals. Accordingly, technological development has been promoted to reduce such noise below the standards of the International Special. Committee on Radio Interference (CISPR) for controlling noise. Resistors, inductors, capacitors, semiconductor elements, and wiring lines between them included in an electric circuit have been devised to reduce noise. However, further reduction of noise is desired.
For example, according to Japanese Patent Application Laid-Open No. 08-191115 (1996), a metal shield plate is disposed on the back surface of a lead frame (a surface opposite to the surface on which a semiconductor element is mounted) to reduce radiation noise by electrostatic shielding.
As described above, according to Japanese Patent Application Laid-Open No. 08-191115 (1996), the metal shield plate is disposed on the back surface of the lead frame, and thus reduction of radiation noise cannot be achieved on a side of the lead frame on which the semiconductor element is mounted.